WASHINGTON — Russell Carpenter owes his life to the ugliest warplane in the Pentagon fleet.

When about 3,000 U.S. soldiers traveling on a dirt road in Iraq came under fire from behind a ridge in the opening weeks of the 2003 American invasion, the retired Air Force chief master sergeant says he called for air support from the only plane that could fly low and slow enough to tell friend from foe: the A-10.

"They would have killed hundreds of our dudes" if it weren't for the firepower of the A-10, with its seven-barrel Gatling gun that sounds like a buzz saw, Carpenter says.

The trust of several generations of soldiers and airmen in the A-10, known as the Warthog for its snout-like nose, has propelled opposition to the Pentagon's plan to retire all 283 of the 1970s-era planes to save $4.2 billion over five years in a time of budget cuts.

The voices of combat veterans have added an extra edge to the hometown lobbying that makes it hard to kill any major weapons program, from tanks the military no longer wants to the troubled new Littoral Combat Ship.

The Defense Department proposal, part of the fiscal 2015 budget request sent to Congress in March, has even become the centerpiece of a political campaign in Arizona, where a former A-10 pilot is running for a U.S. House seat against an incumbent she says hasn't done enough to save the plane. A base in the district is home to the biggest fleet of A-10s, and pilots are trained to fly them there.

In a reflection of efforts by lawmakers to save the plane, the House Armed Services Committee will take initial action on the A-10 tomorrow when it approves its version of the annual defense policy measure. The panel plans to include language barring the department from spending any funds to retire the fleet of planes unless it keeps them in good condition to fly if needed, according to draft legislation released by the panel.

"It is such an emotional issue," said retired Lt. Gen. David Deptula, a former Air Force intelligence chief who heads the Deptula Group, a consulting firm based in Oakton, Virginia. Given the budget constraints, he said in an interview, the decision to retire the plane makes sense.

Top Army officers make clear that they and their troops would miss the protection the A-10 has long provided.

"It's a game-changer," General John Campbell, the Army's vice chief of staff, said at a Senate hearing on March 26. "It's ugly; it's loud. But when it comes in and you hear that 'bvvrr,' it just makes a difference."

The Air Force maintains that retiring the A-10 won't put soldiers' lives at greater risk. The service says newer, faster aircraft — such as the F-16, the F-15E, bombers and, eventually, the new F-35 fighter from Lockheed Martin — can perform the A-10's principal mission of "close air support," striking targets on the ground to help soldiers in a land battle.

"The mission will continue," Gen. Mark Welsh, the Air Force chief of staff, said at an April 10 hearing of the Senate Armed Services Committee. "We'll figure out how to do it better than it's ever been done before with the platforms we have."

The A-10's defenders say that promise rings hollow because other aircraft can't maneuver as close to the ground to home in on enemy forces.

"I wish the Air Force would be more forthright with what it's doing with the A-10," said retired Maj. Gen. Lawrence Stutzriem, a former director of plans, policy and strategy for the North American Aerospace Defense Command.

"We're going to have reduced capability," said Stutzriem, who has flown both the A-10 and the F-16 and is an independent consultant on security in Colorado Springs, Colorado.

The A-10's supporters also question whether the military would commit its costly F-35 to support U.S. troops in ground combat.

"You really think they're going to allow a $200 million airplane to get down in the weeds where's it's extremely vulnerable?" retired Lieutenant Colonel William Smith, an airline pilot who flew the A-10 in Iraq and Afghanistan, said of the F-35 made by Bethesda, Maryland-based Lockheed.

While the A-10 — which the Air Force says cost $18.8 million per plane in today's dollars — is more vulnerable to enemy aircraft than fighters designed for air-to-air combat, a titanium "bathtub" that wraps around the bottom of the cockpit offers better protection against ground fire.

The twin-engine A-10 can fly as slowly as 300 knots (345 miles per hour) without risk of stalling, compared with 450 knots for an F-16 or F-35, and that allows more time to identify and shoot at ground targets, said Colonel Douglas Nikolai, the Air Force's director of operations force management.

The A-10 has a more powerful gun than the fighters. Its Gatling gun, which is 20 feet (6 meters) long and weighs 2.5 tons, can fire more than 1,100 rounds of 30 mm bullets. The F-16 and F-15E have a 20 mm gun that holds fewer than half the bullets. All of the planes have missiles and bombs that can be guided to ground targets.

"There are niche scenarios where the A-10 probably does a better job," Nikolai said in an interview. "In tough budget times, we have to make tough choices. Is it going to cost us lives? That's open for debate."

Nikolai and other Air Force leaders say that as their budget shrinks they can't afford to maintain a single-purpose plane when others can fill the void. Even if Congress were to repeal the automatic budget cuts known as sequestration, the service faces $10.7 billion in reductions from previously planned spending over the next four years.

"It's a very beloved aircraft, and nobody likes the idea of retiring it," Air Force Secretary Deborah Lee James said in congressional testimony in March.

Mark Gunzinger, a former bomber pilot and deputy assistant secretary of defense, said low-flying aircraft may no longer be needed in an age of drones and precision-guided weapons.

"You've got to look at different ways of doing the mission," Gunzinger, a senior fellow at the Center for Strategic and Budgetary Assessments in Washington, said in an interview.

Politically, the Air Force has one advantage in seeking to eliminate the A-10: The plane lacks an active manufacturer and workforce, the core constituency for weapons still being built.

Conceived in the 1970s to destroy Soviet tanks, the A-10 hasn't been produced since 1984, although it's been upgraded, according to GlobalSecurity.org, a defense policy group in Alexandria, Virginia. The plane was built by Fairchild Republic, now part of Northrop Grumman, based in Falls Church, Virginia.

The A-10 does have some economic benefits. Boeing Co. was awarded a $1.1 billion contract in 2007 to put new wings on as many as 173 of the planes at a plant in Macon, Georgia. About 42 have been retrofitted so far, according to the Air Combat Command.

Ellen Buhr, a spokeswoman for Boeing, declined to discuss whether the Chicago-based company is lobbying to save the A-10.

The A-10's political stronghold is Tucson, Arizona. About 83 Warthogs are stationed there at Davis-Monthan Air Force Base, followed by the 48 planes at Moody Air Force Base in Georgia, according to the Air Combat Command.

Ret. Air Force Col. Martha McSally, a Republican, is challenging Democratic Rep. Ron Barber in a Tucson- based district, partly on the issue of saving the A-10, which she flew in Iraq. The homepage of her campaign website shows McSally, who was the Air Force's first female pilot to fly in combat, in uniform with an A-10 in the background.

"The thought we would be at risk of losing the A-10 and losing Davis-Monthan is a really big deal in our community," McSally said in an interview, citing local concerns that the base may be shut down if the A-10s go and aren't replaced.

Barber said McSally's accusation that he's fallen short in championing the A-10 is "totally off-base" and that he's "been on this issue from Day One."

The plane's most outspoken congressional defender is Sen. Kelly Ayotte, R-N.H., a member of the Senate Armed Services Committee. While Ayotte has no Warthogs in her state, her husband flew the A-10 on combat missions in Iraq.

"I'm in for this fight," Ayotte said, pledging to find other savings in the Pentagon budget to compensate for keeping the plane.

If the A-10 is to be saved from retirement, it's likely to be thanks to the loyalty of veterans such as Ayotte's husband and Carpenter, 51, who now lives in Georgia and is a consultant to defense contractors.

"This is absolutely personal," says Carpenter, who won the Bronze Star with a V for Valor for his Iraq service.

With assistance from Roxana Tiron and Jonathan D. Salant in Washington.